diff --git a/Documentation/DocBook/media/dvb/dvbproperty.xml b/Documentation/DocBook/media/dvb/dvbproperty.xml index 28ea62067af6..c10ed0636d02 100644 --- a/Documentation/DocBook/media/dvb/dvbproperty.xml +++ b/Documentation/DocBook/media/dvb/dvbproperty.xml @@ -1,8 +1,35 @@ -
-<constant>FE_GET_PROPERTY/FE_SET_PROPERTY</constant> -This section describes the DVB version 5 extension of the DVB-API, also -called "S2API", as this API were added to provide support for DVB-S2. It was -designed to be able to replace the old frontend API. Yet, the DISEQC and +
+DVB Frontend properties +Tuning into a Digital TV physical channel and starting decoding it + requires to change a set of parameters, in order to control the + tuner, the demodulator, the Linear Low-noise Amplifier (LNA) and to set the + antena subsystem via Satellite Equipment Control (SEC), on satellital + systems. The actual parameters are specific to each particular digital + TV standards, and may change as the digital TV specs evolutes. +In the past, the strategy used were to have an union with the parameters + needed to tune for DVB-S, DVB-C, DVB-T and ATSC delivery systems grouped + there. The problem is that, as the second generation standards appeared, + those structs were not big enough to contain the additional parameters. + Also, the union didn't have any space left to be expanded without breaking + userspace. So, the decision was to deprecate the legacy union/struct based + approach, in favor of a properties set approach. +By using a properties set, it is now possible to extend and support any + digital TV without needing to redesign the API +Example: with the properties based approach, in order to set the tuner + to a DVB-C channel at 651 kHz, modulated with 256-QAM, FEC 3/4 and symbol + rate of 5.217 Mbauds, those properties should be sent to + FE_SET_PROPERTY ioctl: + + DTV_FREQUENCY = 651000000 + DTV_MODULATION = QAM_256 + DTV_INVERSION = INVERSION_AUTO + DTV_SYMBOL_RATE = 5217000 + DTV_INNER_FEC = FEC_3_4 + DTV_TUNE + +NOTE: This section describes the DVB version 5 extension of the DVB-API, +also called "S2API", as this API were added to provide support for DVB-S2. It +was designed to be able to replace the old frontend API. Yet, the DISEQC and the capability ioctls weren't implemented yet via the new way. The typical usage for the FE_GET_PROPERTY/FE_SET_PROPERTY API is to replace the ioctl's were the